Various electrical connectors are known for use in the telecommunications industry to transmit voice, data, and video signals. It is common for some electrical connectors to be configured to include a plug which is connectable to a jack mounted in the wall, or as part of a panel or other telecommunications equipment mounted to a rack or cabinet. The jack includes a housing which holds a plurality of closely spaced contact springs in the appropriate position for contacting the contacts of a plug inserted into the jack. The contact springs of the jack are often mounted to a printed circuit board, either vertically or horizontally. An RJ45 plug and jack connector system is one well known standard including closely spaced contacts.
Crosstalk between the contacts and circuit pathways in telecommunications connectors is a concern. U.S. Pat. Nos. 5,299,956 and 5,700,167 are examples of various connectors including jacks and plugs which attempt to address the problem of crosstalk in the circuit board. It is desired to improve performance of the electrical connectors, such as an RJ45 connector, where crosstalk problems increase as higher frequencies are transmitted through the connector.
Most of the crosstalk problems occurring in a connector, such as an RJ45 connector, is mainly caused by the plug. This crosstalk is produced by the non-periodic or random discharges of crosstalk energy due to the imbalanced capacitance and/or inductance in the plug and the contact springs of a jack. RJ45 types of connectors arc mainly used with balanced twisted pairs of conductors or wires. There is no grounding to shield the crosstalk energy.
One of the known techniques commonly used to solve the crosstalk problem in a connector is to balance the capacitance on the printed circuit board or on a substrate of the connector to minimize or eliminate the leaking energies from the unbalanced capacitance. The known method of reducing crosstalk generally includes forming of a capacitor by using two parallel conductive lines or wires and inducing electromagnetic field to compensate the lesser field produced by the capacitive imbalance in the plug. This method is often referred to as capacitance balancing or capacitive compensation. The known compensation technique is applied at the nearest unbalanced components, which are the contact springs of a jack and the mated RJ45 plug. This technique is very useful for the TIA/EIA category 5 and Enhanced category 5 (5E) connector. However, the crosstalk performance of these connectors is rated only up to 100 MHz. Higher frequencies are in demand in the telecommunication and data transmission industry. The TIA/EIA category 6 connector standards have been proposed to meet the demand. Under the proposed category 6 standards, the connector is required to meet the crosstalk specifications up to 250 MHz, which is about 150% more bandwidth than the category 5's.
In order to meet this specifications, additional compensations or additional parallel conductive lines are needed to be placed on the circuit board at the nearest unbalanced components. It has been found that capacitive compensation only worsens the directivity or equal-level of the far-end crosstalk (FEXT) of the connector because the capacitor formed by two conductive lines has an inductive effect which is not accountable for. Also, it has been found that the additional compensation has a reverse capacitive effect on the near-end crosstalk (NEXT) of the connector. Generally, the far end and the near end are defined according to the two ends of the printed circuit board. The end to which signals are being injected is the near end. The opposite is the far end.
In addition, the natural crosstalk characteristic for short transmission lines, i.e. -20 dB per frequency decade, will be lost if the connector is heavily compensated. This natural crosstalk characteristic is generally required to be maintained in order for a connector to meet the category 6 crosstalk specifications.
Accordingly, the known compensation technique is either insufficient to compensate the crosstalk, or problematic by overcompensating for the crosstalk. The known compensation technique has been considered ineffective when applied to the development of a category 6 or a category 6 type of connector, and particularly, it is unable to meet the crosstalk specifications up to 250 MHz.
Thus, there is a need for a connector including an improved crosstalk compensation technique for a printed circuit board. Further, there is a need for a connector with balanced capacitance and/or inductance on the printed circuit board to minimize or eliminate crosstalk in the connector.